Convert CONFIG_ENV_OVERWRITE to Kconfig

This converts the following to Kconfig:
   CONFIG_ENV_OVERWRITE

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Rerun migration, remove some comments]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/lx2160aqds_tfa_SECURE_BOOT_defconfig b/configs/lx2160aqds_tfa_SECURE_BOOT_defconfig
index 1166d69..f2faf7b 100644
--- a/configs/lx2160aqds_tfa_SECURE_BOOT_defconfig
+++ b/configs/lx2160aqds_tfa_SECURE_BOOT_defconfig
@@ -35,6 +35,7 @@
 CONFIG_OF_CONTROL=y
 CONFIG_OF_LIST="fsl-lx2160a-qds-3-x-x fsl-lx2160a-qds-7-x-x fsl-lx2160a-qds-19-x-x fsl-lx2160a-qds-20-x-x fsl-lx2160a-qds-3-11-x  fsl-lx2160a-qds-7-11-x fsl-lx2160a-qds-7-11-x fsl-lx2160a-qds-19-11-x fsl-lx2160a-qds-20-11-x"
 CONFIG_MULTI_DTB_FIT=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_DM=y
 CONFIG_SATA_CEVA=y